The present invention relates to a method and arrangement for resolving performance feature interactions in a communication system with switching control and performance feature control decoupled from one another, in what are called IN-type architectures (in this context, IN means Intelligent Networks).
Prior art switching systems support a plurality of performance features. These features include auxiliary telecommunication services, such as for example:
Call forwarding CFU; PA1 Call forwarding when busy CFBS; PA1 Call forwarding when idle CFNR; PA1 Speed dialing SD; PA1 Selective station guarding TCS; PA1 Callback CC, alternation CA, transfer CT; PA1 Call waiting CO, accept waiting call TCO; PA1 Conference CONF; and PA1 Automatic callback when busy ARBS.
Two types of performance features are to be distinguished. On the one hand there are performance features that are explicitly activated (FReq) and are called in response to reception of an initiating event. The feature CFU is an example of this type. On the other hand, there are performance features that are called directly (via FReq) without having been activated previously, such as when activation and calling coincide. The features CONF or CC are examples of this. All performance features can be requested using an "activation" message FReq.
In processor-controlled switching installations, performance features are realized within the switching control sequences. These switching control sequences, also called switching software, contain the call controlling as well as the performance features. The performance features are combined with the call controlling, as well as with one another. This leads to a high degree of software complexity, whereby the software structure becomes inflexible with respect to the introduction of newer performance features. In order to shorten the long introduction times for new performance features, consideration has been given to the possibility of realizing the parts of the control sequences, that were previously dependent on one another, as separated from one another in independent modules that respectively have a fixed external interface. Approaches to the separation of the performance feature control from the switching control are pursued in the context of the standardization processes relating to intelligent networks "Intelligent Network" in ITU-T SG 11. On this subject, see the CCITT guidelines "New Recommendation Q.1214, Distributed Functional Plane for Intelligent Network CS-1, COM XI-R212-E", pages 7 to 69, as well as appendix pages 7 to 9.
A cleanly structured switching architecture results from the decoupling of the performance feature control from the switching control, which is reduced to its basic functionality. This switching architecture is constructed in a very modular fashion, and allows the rapid introduction of new performance features. Moreover, a development independent of the performance features and the call control is enabled by the separation of the performance features.
A structure of this sort divides a switching system or, respectively, the switching software into a basic switching system and a performance feature system, i.e., the switching control and the performance feature control are decoupled from one another. The main components of a basic switching system are a call control, a database and a plurality of performance feature control components. The call control is reduced to its fundamental tasks, the setting up and clearing down of connections or, respectively, calls, and is thus designated the basic call control. The performance feature control components form a set of functions, via which access can take place to the call objects and via which calls can thus be manipulated.
The performance features themselves are contained in the performance feature system, which communicates with the basic switching system via a protocol. The basic call control of the basic switching system has the job of carrying out the setting up and clearing down of calls or, respectively, of the associated connections according to subscriber requests. In the context of its normal operating sequence, it thus handles a two-subscriber call. In addition, mechanisms are provided for the reporting of determined events to the performance feature control. The basic switching system can control a call between two subscribers without influence of the performance feature system; i.e., it is independent of the setting up and clearing down of two-subscriber calls. A two-subscriber call exists between two communication terminal apparatus respectively allocated to subscriber terminal units. Each of the terminal apparatus respectively has a connection that creates the relation between a communication terminal apparatus and the call. A state automaton is respectively allocated to each connection. The connections are linked with one another via the call.
Determined processes, triggered by external events, take place between the states of the state automata. Such events are subscriber/network messages or internal messages, namely messages between the two connections of a call. "Performance feature interactions" take place between individual performance features that are simultaneously activated and have been called or are to be called. The term "performance feature interactions" hereby comprises all interactions connected with the desired operation of a performance feature LM. These are interactions of the performance feature with its environment, i.e. other performance features, but also other calls (activations) of the same performance feature.
Impermissible performance feature interactions can lead to disturbances in the switching sequence. It is thus recommended that the performance feature interactions be resolved in order to avoid such disturbances.